Analysis of the scenario of a heavy accident in the storage pools for spent nuclear fuel isf-1 — Науково-технічний журнал «Техногенно-екологічна безпека»

Analysis of the scenario of a heavy accident in the storage pools for spent nuclear fuel isf-1

S. Azarov, V. Sydorenko, A. Zadunay

DOI: 10.5281/zenodo.1296272

Received: 24 May 2018

Accepted: 15 June 2018

Published online: 18 June 2018

ABSTRACT

Approaches to simulation of the storage pools (SP) for ISF-1 and the results of thermal-hydraulic calculation of scenarios of severe accidents in SP. In the course of the work, the scenario of a severe accident after an earthquake with a prolonged de-energization and the formation of a leak through the metal cladding of the bottom of the SP was considered. Based on the results of computational analyzes, the dynamics of the main processes accompanying the development of a severe accident in the SP of this type have been determined. Key results of calculations: growth rate of mean volume water temperature in the basin at the initial stage of the accident development is 0.6°С/h; when the water level in the upper part of the fuel assembly drops to 51800 s (~14.4 h), the complete dehumidification of SP takes place approximately 64800 s (~18 h) the fuel element temperature reaches 1473 K at 66500 s (~18.5 h), and the fuel temperature is 2813 K after 77400 s (21.5 h) after the start of the accident. When the fuel cladding temperature rises above 1100 K, they begin to be oxidized by water vapor with an intense formation of hydrogen and the release of heat, and when hydrogen is burned, an energy equal to an average of about 260 kJ/mol of reagent, with an explosion of ~ 105 moles of hydrogen formed, more than 3 · 107 kJ energy will be released, and this energy will be scattered as a pulse with a duration of a fraction of a second. Further development of a severe accident can cause destruction of the SP, with the penetration of the bottom. The ingress of hydrogen into the air atmosphere will lead to the formation of an explosive mixture, create conditions for the ignition, explosion, destruction of ISF-1 and the release of radioactivity beyond its limits.

The obtained results of the quantitative analysis can be used to improve the existing design models of SP and to obtain more reliable calculation data for the development of emergency processes in SP of power units of NPPs.

Keywords: storage pools, calculation model, severe accident, fire, explosion.

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